Display device

Abstract

In an image display device, each pixel includes a drive transistor for driving a light emitting element, a capacitive element which is connected between a signal line and a control electrode of the drive transistor, and a reset switching element. The reset switching elements of all pixels are turned off within a light emission period, and a PWM signal is supplied to a signal line from a drive circuit. A cycle of the PWM signal in a low brightness display mode is shorter than a cycle of the PWM signal in a standard brightness display mode. Due to such a constitution, the constitution of a drive circuit can be simplified, and it is possible to control light emission brightnesses of respective pixels of red, green and blue over a wide range from high brightness to low brightness while taking a balance among the light emission brightnesses.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The present application claims priority from Japanese application JP 2008-208614 filed on Aug. 13, 2008, the content of which is hereby incorporated by reference into this application.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a display device, and more particularly to a technique which is effectively applicable to an organic EL display device which uses organic EL elements or the like.[0004]2. Description of the Related Art[0005]Although cathode ray tubes (CRTs) have been a mainstream of the display devices conventionally, recently, a demand for flat display devices has been increasing as display devices which replace the cathode ray tubes. Particularly, an organic EL (Electro Luminescence) display device which uses organic EL elements such as OLED (Organic Light Emitting Diodes) possesses excellent properties such as small power consumption, light weight, small thickness, excellent mo...

AI Technical Summary

Benefits of technology

The present invention provides a display device that can control the brightness of pixels in different modes, while taking into account the irregularities of brightness between pixels. Compared to existing display devices, the invention simplifies the drive circuit and reduces the cost. The display device includes a drive circuit that supplies a video signal and a PWM signal to pixels, and a reset switching element which controls the brightness of the pixels. The invention also has multiple brightness display modes, and the cycle of the PWM signal is set shorter in a low brightness display mode than in a standard brightness display mode.

Problems solved by technology

Further, the display devices disclosed in patent document 2 and patent document 3 perform the gamma correction and hence, each display device requires an A / D converter, a D / A converter and correction memories thus giving rise to a drawback that the display devices has the complicated constitution and is costly.

Still further, in patent document 3, irregularities of local characteristics such as the brightness irregularities between respective pixels are not taken into consideration and hence, the display device disclosed in patent document 3 cannot overcome the irregularities of local characteristics such as brightness irregularities between the respective pixels.

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